This is a common palindrome example in java.

reverseString.java

public class reverseString{
  
  public static void main (String[] args){
    
    String str = new String(args[0]);
    int x = str.length();
    char[] strArray = new char[x];
    
    for(int i = 0; i < str.length(); i++){
      strArray[i] = str.charAt(--x);
    }
    
    String finalString = new String(strArray);
    System.out.println(strArray);
  }
}